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SubjectRe: [patch] cciss: Fix race between disk-adding code and interrupt handler


> On Mon, Apr 14 2008, scameron@beardog.cca.cpqcorp.net wrote:
> >
> >
> > Fix race condition between cciss_init_one(), cciss_update_drive_info(),
> > and cciss_check_queues(). cciss_softirq_done would try to start
> > queues which were not quite ready to be started, as its checks for
> > readiness were not sufficiently synchronized with the queue initializing
> > code in cciss_init_one and cciss_update_drive_info. Slow cpu and
> > large numbers of logical drives seem to make the race more likely
> > to cause a problem.
>
> Hmm, this seems backwards to me. cciss_softirq_done() isn't going to
> start the queues, until an irq has triggered for instance. Why isn't the
> init properly ordered instead of band-aiding around this with a
> 'queue_ready' variable?
>

Each call to add_disk() will trigger some interrupts,
and earlier added disks may cause the queues of later,
not-yet-completely added disks to be started.

I suppose the init routine might be reorganized to initialize all
the queues, then have second loop call add_disk() for all
of them. Is that what you had in mind by "properly ordered?"

Disks may be added at run time though, and I think this tears
down all but the first disk, and re-adds them all, if I remember
right, so there is some complication there to think about.

-- steve

On Mon, Apr 14, 2008 at 07:05:05PM +0200, Jens Axboe wrote:
> --
> Jens Axboe
>


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